This invention relates generally to surgical instruments, and, more particularly, to a surgical device for ultrasonic fragmentation or emulsification of soft tissues of a patient.
Liposuction is a surgical procedure for altering the human form, specifically by removal of localized deposits of fat tissues that are unresponsive to diet or exercise. The procedure is also known as suction lipectomy, lipolysis, and more recently as body contour surgery, body sculpting surgery, or suction-assisted liposuction. It is most often performed by plastic surgeons, although dermatologists, gynecologists, and other surgical specialties also perform such procedures.
A liposuction procedure is typically accomplished by inserting a small cannula through an incision in the skin, applying a suction source to the end of the cannula that remains outside of the body, and forcing the working end of the cannula forward and backward in the layer of fatty tissue. The fatty tissue is torn, crushed, or avulsed, and is then aspirated through small openings along the sides of the cannula near the tip and then through a central lumen in the cannula to a tissue canister placed in-line with the cannula and the suction source. The procedure may involve multiple incisions and many passes of the cannula in each incision to achieve the desired cosmetic effect for the patient. No ultrasonic energy is used in this procedure.
A liposuction cannula is typically a small metal tube with a blunt, closed end at the tip of the cannula. The blunt, closed end at the tip of the cannula is intended to minimize damage to tissues as the device is thrust forward. Small openings along the sides of the cannula near the tip create passages between the tissue and the central lumen of the cannula, which is in fluid communication with a suction source, so that tissue and fluids can be aspirated from the patient's body. In general, the suction causes the adipose tissue to be sucked into the small openings along the sides of the cannula, and the blunt dissection as provided by the surgeon's manipulation of the cannula, then tears the tissue. The fragments and released fluids are then aspirated through the openings along the sides of the cannula and then through the central lumen of the cannula.
The liposuction procedure can be traumatic for the patient. The liposuction cannula does not discriminate between adipose tissue and other tissues such as nerves, blood vessels, or lymph tissues. The mechanical disruption of those tissues by the liposuction cannula may result in, among other things, bleeding, bruising, temporary numbness, or swelling. Further, the final cosmetic result achieved for the patient is a function of the skill of the surgeon, the patient, and the type of surgical instrumentation used in the surgery. Liposuction cannulae used in the liposuction procedure may remove more adipose tissue from one area than another area in the patient, resulting in skin contour irregularities and a final cosmetic result for the patient that is not smooth or uniform or desired.
Therefore, there is a need to improve the design of liposuction cannulae to help the surgeon to better discriminate between adipose tissue and other tissues such as nerves, blood vessels, and lymph tissues, so that the adipose tissues can be fragmented and removed while the remaining tissues are damaged as little as possible or not at all. Further, there is a need to improve the design of current liposuction cannulae such that adipose tissue is removed in a uniform and predictable manner such that an improved cosmetic result is achieved for the patient.
Recently, several instruments have combined ultrasonic vibrations and the liposuction cannula to improve upon the tissue discrimination capability of the liposuction cannula and to provide an instrument, which removes adipose tissue more uniformly than current liposuction cannulae. This procedure is commonly referred to as ultrasound-assisted lipoplasty. In a typical ultrasound-assisted lipoplasty procedure, an ultrasonically vibrating cannula is inserted through an incision in the patient's skin and passed forward and backward through the adipose tissue layer. The ultrasonically vibrating cannula preferentially fragments or emulsifies the adipose tissues, which are then typically aspirated through a central lumen in the ultrasonically vibrating cannula. Consequently, the other tissues such as nerves, vessels, and lymph tissues remain generally undisturbed.
Initial experiences with the ultrasound-assisted lipoplasty procedure have been mixed. A comparison of the suction-assisted liposuction and ultrasound-assisted lipoplasty approaches with currently available surgical instruments for both procedures was recently given in Ultrasound-Assisted Lipoplasty Resource Guide, published in PlasticSugery News, a publication of The American Society of Plastic and Reconstructive Surgeons, 1997. In the article the author cites the disadvantages of the current ultrasound-assisted lipoplasty procedure compared to the suction-assisted liposuction procedure as: 1) burns of the skin are possible, 2) longer incisions are needed, 3) seromas are more common, 4) longer operating times, and 5) greater expense. Thus, current ultrasound-assisted lipoplasty surgical systems for fragmentation and aspiration of adipose tissues are more costly and slower than the suction-assisted liposuction procedure and have the potential to damage tissues beyond that of suction-assisted liposuction, including burns of the skin and seroma formation. There is, therefore, a need to increase patient safety, to increase the speed of the ultrasound-assisted lipoplasty procedure, and to minimize the potential for burns or seroma formation.
An ultrasonic probe for soft tissue fragmentation may be hollow, in which case the instrument may be referred to as an ultrasonic cannula or it may be solid. The distal end of an ultrasonic probe experiences small rapid excursions along an axis that passes through the proximal end and the distal end of the ultrasonic probe. A maximum excursion of 350 .mu.m peak-to-peak at 23 kHz has been obtained in a commercially available ultrasonic aspirator for ultrasonic surgery, e.g., the CUSA of Valleylab Inc., Boulder, Colo.
An ultrasonic handpiece typically has a handle with an ultrasonic motor, an ultrasonic horn, and an ultrasonic probe. At locations along the ultrasonic probe referred to as `vibratory nodes` the elastic stress and strain will have maximum values and there will be no motion of the ultrasonic probe relative to the handle of the ultrasonic handpiece. At locations along the ultrasonic probe referred to as `vibratory loops` the elastic stress and strain will have minimum values and there will be maximum motion of the ultrasonic probe relative to the handle of the ultrasonic handpiece. The `vibratory nodes` become hot as the ultrasonic probe vibrates at the resonant ultrasonic frequency because the metallic material of the ultrasonic probe is being continually worked as it is stretched and released many thousand times per second. In an ultrasound-assisted lipoplasty procedure tissue surrounds and contacts the ultrasonic probe along its length. Thus, tissue contact with a vibratory node after the probe has been in operation can cause a tissue burn. A tissue burn may also occur for any tissue that contacts a vibratory loop because of the frictional heat generated between the tissue and the rapidly moving ultrasonic probe at the vibratory loop. Further, the heat generated by the ultrasonic motor in the ultrasonic handpiece may be conducted from the ultrasonic motor through the ultrasonic horn to the ultrasonic probe, further increasing the temperature of the ultrasonic probe. The combination of these three sources of heat can and will cause tissue burns, most particularly at or near the vibratory loops.
Many patents disclose improvements and solutions for ultrasound-assisted lipoplasty instruments for removal of adipose tissue from the human body. U.S. Pat. No. 4,886,491 to Parisi has a method of removing fatty tissue from a patient using an ultrasonic probe and its energy application to melt at least some of the fatty tissue. U.S. Pat. No. 5,244,458 to Takasu has an ultrasonic handpiece with a hollow cannula with a plurality of suction openings in that cannula. U.S. Pat. No. 5,236,414 also to Takasu has an ultrasonic handpiece with a tip having a tubular body and a suction passage. U.S. Pat. No. 5,419,761 to Narayanan has an ultrasonic handpiece with a rigid tube with an axially extending lumen. U.S. Pat. No. 5,514,086 to Parisi has an ultrasonic handpiece with a probe and a tip on the probe. The tip has an acoustic impedance substantially greater than that of the probe. U.S. Pat. No. 5,527,273 to Manna has an ultrasonic lipectomy probe with an enlarged head on the distal end and a longitudinally extending channel in the probe. U.S. Pat. No. 5,123,903 to Quaid has an ultrasonic handpiece and horn, the ultrasonic horn protected by a sheath which forms an annular passage operarable to conduct fatty tissue aspirate from the distal end of the ultrasonic horn. The inner diameter of the sheath in this patent is sufficiently larger than the outer diameter of the ultrasonic horn so that the annular passage is functional for the passage of aspirated tissue and fluids, thus significantly increasing the overall diameter of the sheath. Further, the sheath terminates at the tip of the ultrasonic probe, which is a vibratory loop, thus shielding the tip of the ultrasonic probe and creating a dragging sensation for the surgeon. The end of the sheath is open and permits the flow of material into the annular passage. U.S. Pat. No. 4,808,154 to Freeman has cylindrical sleeve with at least one longitudinal rib member operable to conduct a lens flushing solution to the distal end of the ultrasonic probe. U.S. Pat. No. 3,805,787 to Banko has an ultrasonic handpiece and probe with a shield of metallic material, the shield and probe, like many of the subsequent patent efforts, are such as to be operable for the delivery of irrigation fluid to the distal end of the probe or for the removal of aspirate from the distal end of the probe. U.S. Pat. No. 5,421,829 to Olichney has an ultrasonic handpiece with a flue that surrounds a tool to direct irrigant and coolant flow thereabout.
The last four patents cited above disclose sleeves which protectively surround the ultrasonic probe, each sleeve operable for either the delivery an irrigation fluid to the distal end of the ultrasonic probe or for the removal of tissue aspirate from the distal end of the ultrasonic probe in the space created between the sleeve and the ultrasonic probe. These designs have three fundamental problems. First, when irrigation fluid or tissue aspirate is present in the space between the sleeve and the ultrasonic probe it significantly increases the power required by the ultrasonic motor to maintain a selected level of vibration amplitude due to the frictional contact between the ultrasonic probe and the irrigation fluid or tissue aspirate at the vibratory loops along the ultrasonic probe. This increased power requirement is expensive and cumbersome while causing the handle to quickly warm and become too hot to hold in a bare hand. Second, these sleeve designs terminate approximately at the distal end of the ultrasonic probe, which is a vibratory loop, and therefore have an outside diameter of the sleeve is larger than the outside diameter of the ultrasonic probe. This shielding of the ultrasonic probe makes passage of the ultrasonic probe and sleeve through the tissue difficult, creating a dragging sensation for the surgeon and generating trauma to the patient. Third, to achieve reasonable performance from either an irrigation system or an aspiration system that utilizes the space between the sleeve and the ultrasonic probe there must be sufficient clearance between the two so that resistance to flow is not too large. This increases the overall diameter of the sleeve so that a significantly larger incision is required in the patient.
While some of the patented devices have disclosed and claimed improvements and solutions to ultrasound-assisted lipoplasty instruments, none address or appreciate the needs or address the problems discussed above. Specifically none address the need for a sleeve to protect the patient from burns while minimizing the power required by the ultrasonic motor and while minimizing the diameter of the sleeve to minimize the drag in the tissue and the size of the incision in the patient.